Disposable products such as facial tissue, sanitary tissue, paper towels, and the like are typically made from one or more webs of paper. If the products are to perform their intended tasks, the paper webs from which they are formed must exhibit certain physical characteristics. Among the more important of these characteristics are strength, softness, and absorbency. Strength is the ability of a paper web to retain its physical integrity during use. Softness is the pleasing tactile sensation the user perceives as the user crumples the paper in his or her hand and contacts various portions of his or her anatomy with the paper web. Softness generally increases as the paper web stiffness decreases. Absorbency is the characteristic of the paper web which allows it to take up and retain fluids. Typically, the softness and/or absorbency of a paper web are increased at the expense of the strength of the paper web. Accordingly, papermaking methods have been developed in an attempt to provide soft and absorbent paper webs having desirable strength characteristics.
Processes for the manufacture of paper products can generally involve the preparation of aqueous slurry of cellulosic fibers and subsequent removal of water from the slurry while contemporaneously rearranging the fibers to form an embryonic web. Various types of machinery can be employed to assist in the dewatering process. A typical manufacturing process employs the aforementioned Fourdrinier wire papermaking machine where paper slurry is fed onto a surface of a traveling endless wire where the initial dewatering occurs. In a conventional wet press process, the fibers are transferred directly to a capillary de-watering belt where additional de-watering occurs. In a structured web process, the fibrous web is subsequently transferred to a papermaking belt where rearrangement of the fibers is carried out. Alternatively, air-laid processes for the formation of such structures are also possible.
After the initial formation of the web, which later becomes the cellulosic fibrous structure, the papermaking machine transports the web to the dry end of the machine. In the dry end of a conventional machine, a press felt compacts the web into a single region of cellulosic fibrous structure having uniform density and basis weight prior to final drying. The final drying can be accomplished by a heated drum, such as a Yankee drying drum, or by a conventional de-watering press. Through air drying can yield significant improvements in consumer products. In a through-air-drying process, the formed web is transferred to an air pervious through-air-drying belt. This “wet transfer” typically occurs at a pick-up shoe, at which point the web may be first molded to the topography of the through air drying belt. In other words, during the drying process, the embryonic web takes on a specific pattern or shape caused by the arrangement and deflection of cellulosic fibers. A through air drying process can yield a structured paper having regions of different densities. This type of paper has been used in commercially successful products, such as Bounty® paper towels and Charmin® bath tissue. Traditional conventional felt drying does not produce a structured paper having these advantages. However, it would be desirable to produce a structured paper using conventional drying at speeds equivalent to, or greater than, a through air dried process.
Once the drying phase of the papermaking process is finished, the arrangement and deflection of fibers is complete. However, depending on the type of the finished product, paper may go through additional processes such as calendering, softener application, and converting. These processes tend to compact the dome regions of the paper and reduce the overall thickness. Thus, producing high caliper finished paper products having two physically distinct regions requires forming cellulosic fibrous structures in the domes having a resistance to mechanical pressure.
It would be advantageous to provide a wet pressed paper web having increased strength and wicking ability for a given level of sheet flexibility. It would be also be advantageous to provide a non-embossed patterned paper web having a relatively high density continuous network, a plurality of relatively low density domes dispersed throughout the continuous network, and a reduced thickness transition region at least partially encircling each of the low density domes.